Typical offshore structures such as semi-submersible or tension-leg platforms, or a spar, comprise a hull part that extends into the water, and which has sufficient buoyancy to support a work area or platform above the water surface. The hull of a platform typically comprises a structure of a plurality of horizontal pontoon elements connected by nodes, which supports a plurality of column elements vertically upstanding from the nodes, which column elements in turn support the work platform or topside above the surface of the water. In general, the size and configuration of the pontoons and the size, number and shape of columns are governed by the size and weight of the work platform and associated payload to be supported. Such a platform is for example disclosed in International patent application publication No. WO 2010/042937.
During operation of an offshore platform it can be needed to store chemicals in substantial quantities, such as for use during a drilling operation, for a treatment of the subsea formation, or for enhanced oil recovery. Certain such chemicals can be corrosive. Over the service life of such platform of typically many years, different chemicals may need to be stored.
There is a need in the art for an improved storage for liquid on a buoyant offshore structure.